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  <title>Document</title>
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  <script>
    // let num = 10
    // console.log(num)
    // 1. 函数的声明   
    function sayHi() {
      console.log('hi~~~')
    }
    // 2. 函数调用   函数不调用，自己不执行
    sayHi()
    sayHi()
    sayHi()
  </script>
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